1. Field of the Invention
Embodiments of the present invention relate to compositions and methods for removing a conductive material from a substrate.
2. Background of the Related Art
Reliably producing sub-half micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the limits of circuit technology are pushed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on processing capabilities. Reliable formation of interconnects is important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates and die.
Multilevel interconnects are formed using sequential material deposition and material removal techniques on a substrate surface to form features therein. As layers of materials are sequentially deposited and removed, the uppermost surface of the substrate may become non-planar across its surface and require planarization prior to further processing. Planarization or “polishing” is a process where material is removed from the surface of the substrate to form a generally even, planar surface. Planarization is useful in removing excess deposited material, removing undesired surface topography, and surface defects, such as surface roughness, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials to provide an even surface for subsequent photolithography and other semiconductor processes.
Electrochemical mechanical polishing (ECMP) is one method of planarizing a surface of a substrate. ECMP removes conductive materials, such as copper, from a substrate surface by electrochemical “anodic” dissolution and optionally reduced mechanical abrasion compared to conventional chemical mechanical planarization (CMP) processes. A typical ECMP system includes a substrate support and two electrodes disposed within a polishing composition containment basin. During the ECMP process the substrate is in electrical contact with an electrode, and generally becomes an anode during the anodic dissolution process steps. In operation, metal atoms on a surface of a substrate are ionized by an electrical current from a power source, such as a voltage source connected to the two electrodes. The metal ions dissolve into the surrounding polishing composition.
Due to the push for high tool throughput, processed substrates per hour, the goal in ECMP type processes is to maximize the electrochemical dissolution rate of the desired material from the surface of the substrate. However, ECMP processes typically have been observed to have reduced removal rates compared to conventional chemical mechanical polishing processes. Modifying the processing conditions, such as increasing pressure between a substrate and polishing pad and increasing processing time, to improve removal rate have not proven to be satisfactory in increasing removal rates and in some instances, such modifications tend to increase dishing and damage to the substrate . For example, increased polishing pressure on substrates containing low dielectric constant (low k dielectric) materials have been observed to form defects in the deposited material, such as delamination or scratches from increased shear forces.
Therefore, there is a need for compositions and methods for removing conductive material from a substrate that minimizes damage to the substrate during planarization.